objects disappear when rendered
I'm not quite sure why this causes a problem, but this happens because your 'floor' object is scaled to 0 on the 'Z' axis. Selecting the 'floor' and doing Ctrl+A> Scale will 'apply' the scale, which resets the current scale back to 1 but doesn't change the object appearance.

You can see a detailed explanation of the difference between scaling in edit mode vs object mode here.